JP5759718B2 - Plasma processing equipment - Google Patents

Description

  The present invention relates to a plasma processing apparatus.

  2. Description of the Related Art Conventionally, in a manufacturing process of a semiconductor device, a plasma processing apparatus that performs various processes such as etching and film formation by applying plasma to a substrate (for example, a semiconductor wafer) disposed on a mounting table in a processing chamber. It is used. Moreover, as such a plasma processing apparatus, an upper electrode is disposed on a ceiling portion of a processing chamber so as to face a mounting table on which a substrate is mounted, and a capacitor having a mounting table as a lower electrode and a pair of counter electrodes A coupled plasma processing apparatus is known.

  In the above capacitively coupled plasma processing apparatus, the high frequency power applied between the upper electrode and the lower electrode is higher than that of the first high frequency power for generating plasma and the first high frequency power. There is known a configuration in which a low-frequency second high-frequency power for ion attraction is applied to a mounting table as a lower electrode.

  Furthermore, a plasma processing apparatus configured to apply high-frequency power to the lower electrode and to apply a DC voltage to the upper electrode is also known. Further, in the plasma processing apparatus for applying a DC voltage to the upper electrode in this way, when a ceramic coating or the like is applied to the ground for a high frequency, a DC voltage ground member for constituting a ground (ground electrode) for the DC voltage is provided. It is necessary to provide it separately. For this reason, a conductive ring-shaped member, for example, a silicon ring-shaped member, is installed as a DC voltage ground member so as to surround the mounting table so that the ring-shaped member is exposed in the processing chamber. It has been known. Further, it is known that the silicon ring-shaped member is formed by fusing a plurality of arc-shaped members by fusion bonding or the like (see, for example, Patent Document 1).

JP 2010-114313 A

  As described above, in the plasma processing apparatus configured to apply high-frequency power to the lower electrode and apply a DC voltage to the upper electrode, a DC voltage ground member acting as a ground for the DC voltage is provided in the processing chamber. Installed to be exposed. In the plasma processing apparatus configured as described above, the present inventors have investigated in detail, and the uniformity of processing in the circumferential direction of the substrate depends on the installation state of the conductive ring-shaped member or the like as the DC voltage ground member. It has been found that there is a case where the process deteriorates and the process may be biased. Such a process bias due to the installation state of the conductive ring-shaped member must be corrected by once opening the processing chamber to the atmosphere and adjusting the installation state of the conductive ring-shaped member. However, there was a problem that it required labor and led to a decrease in productivity.

  The present invention has been made in response to the above-described conventional circumstances, and can easily correct the processing bias due to the installation state of the DC voltage ground member serving as the ground with respect to the DC voltage applied to the upper electrode, An object of the present invention is to provide a plasma processing apparatus capable of efficiently performing uniform processing.

One aspect of the plasma processing apparatus of the present invention includes a processing chamber for forming a processing space therein, a lower electrode disposed in the processing chamber and serving as a mounting table on which a substrate to be processed is mounted, and the processing An upper electrode disposed in the chamber so as to face the lower electrode; a high-frequency power source for applying high-frequency power to the lower electrode; and a DC power source for applying a DC voltage to the upper electrode; A processing gas supply mechanism for supplying a processing gas to be plasmatized into the processing space, and an overall shape formed from a conductive material in a ring shape, and at least a part of the processing space is exposed to the processing space. A DC voltage ground member for forming a ground potential with respect to the DC voltage applied to the upper electrode, and moving the DC voltage ground member up and down A plurality of vertically moving mechanism to the ground state of pressure ground member is adjustable, and the focus ring disposed to surround the periphery of the target substrate disposed on the lower electrode, the outer periphery of the focus ring The DC voltage ground member is disposed on a side surface of the lower electrode so as to surround the lower electrode at a position lower than the cover ring. Sometimes electrically floating or grounded .

  According to the present invention, it is possible to easily correct the process bias due to the installation state of the DC voltage ground member that becomes the ground with respect to the DC voltage applied to the upper electrode, and to perform the uniform process efficiently. A plasma processing apparatus can be provided.

The figure which shows typically schematic structure of the plasma etching apparatus which concerns on embodiment of this invention. The figure which shows typically the principal part structure of the plasma etching apparatus of FIG. The figure which shows typically the principal part structure of the plasma etching apparatus of FIG. The graph which shows the result of having investigated the influence which the grounding state of the ground member for DC voltage has on the uniformity of processing. The graph which shows the result of having investigated the influence which the grounding state of the ground member for DC voltage has on the uniformity of processing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a plasma etching apparatus 10 as a plasma processing apparatus according to the present embodiment.

  The plasma etching apparatus 10 is hermetically configured and includes a processing chamber 11 that forms a processing space PS therein. The processing chamber 11 has a cylindrical shape, and is made of, for example, aluminum having an anodized film formed on the surface thereof. In the processing chamber 11, a columnar mounting table 12 that horizontally supports a semiconductor wafer W as a substrate to be processed is provided.

  An inner wall side surface of the processing chamber 11 is covered with a side wall member 13, and an inner wall upper surface of the processing chamber 11 is covered with an upper wall member 14. The side wall member 13 and the upper wall member 14 are made of, for example, aluminum, and the surface facing the processing space PS is coated with yttria or an anodized film having a predetermined thickness. Since the processing chamber 11 is electrically grounded, the side wall member 13 and the upper wall member 14 are at ground potential.

  The mounting table 12 is formed on a conductive material 15 made of a conductive material, for example, aluminum, a side surface covering member 16 made of an insulating material that covers the side surface of the conductive material portion 15, and the side surface covering member 16. The enclosure member 17 made of quartz (Qz) to be placed and the placement base 15 a made of an insulating material and positioned below the conductor portion 15 are provided.

  Inside the processing chamber 11, an exhaust functioning as a flow path for exhausting the processing gas introduced into the processing space PS between the inner wall of the processing chamber 11 and the side surface of the mounting table 12 to the outside of the processing chamber 11. A flow path 18 is formed. An exhaust plate 19 that is a plate-like member having a large number of ventilation holes is disposed in the exhaust flow path 18. The exhaust plate 19 partitions the exhaust flow path 18 and the exhaust space ES, which is the lower space of the processing chamber 11. A rough exhaust pipe 20 and a main exhaust pipe 21 are opened in the exhaust space ES. A dry pump (not shown) is connected to the rough exhaust pipe 20, and a turbo molecular pump (not shown) is connected to the main exhaust pipe 21. ing. With these dry pump and turbo molecular pump, the processing space PS can be set to a reduced pressure atmosphere of a predetermined pressure.

  On the other hand, a loading / unloading port 44 for the semiconductor wafer W is provided on the side wall of the processing chamber 11. The loading / unloading port 44 is provided with a gate valve 46 that opens and closes the loading / unloading port 44.

  A first high frequency power supply 22 is connected to the conductor portion 15 of the mounting table 12 via a first matching unit 23. The first high-frequency power source 22 is for generating plasma, and supplies high-frequency power of a relatively high predetermined frequency (27 MHz or more, for example, 40 MHz) to the conductor portion 15. The first matching unit 23 reduces the reflection of the high frequency power from the conductor portion 15 and increases the supply efficiency of the high frequency power to the conductor portion 15.

  In addition, a second high frequency power source 24 is further connected to the conductor portion 15 via a second matching unit 25. The second high-frequency power source 24 is for ion attraction (bias), and uses a high-frequency power having a predetermined frequency (13.56 MHz or less, for example, 3.2 MHz) lower than the high-frequency power supplied by the first high-frequency power source 22. It supplies to the conductor part 15.

  An electrostatic chuck 27 having a structure in which an electrode plate 26 is housed in a dielectric is disposed on the mounting table 12. An electrostatic chuck DC power supply 28 is electrically connected to the electrode plate 26 of the electrostatic chuck 27. By applying a DC voltage from the electrostatic chuck DC power supply 28 to the electrode plate 26, the semiconductor wafer W is attracted and held on the upper surface of the electrostatic chuck 27 by a Coulomb force or a Johnson-Rahbek force. Yes.

In addition, an annular focus ring 29 is disposed on the top of the mounting table 12 so as to surround the semiconductor wafer W sucked and held on the upper surface of the mounting table 12. The focus ring 29 is made of silicon (Si), silica (SiO ₂ ), silicon carbide (SiC), or the like. In addition, an annular cover ring 30 made of quartz that protects the side surface of the focus ring 29 is disposed around the focus ring 29.

  In the mounting table 12, for example, an annular refrigerant chamber 31 extending in the circumferential direction is provided. A refrigerant having a predetermined temperature, for example, cooling water or a Galden (registered trademark) liquid, is circulated and supplied to the refrigerant chamber 31 from a chiller unit (not shown) via a refrigerant pipe 32. The processing temperature of the semiconductor wafer W attracted and held on the upper surface is controlled.

  A plurality of heat transfer gas supply holes 33 are opened on the suction surface on the top surface of the mounting table 12 on which the semiconductor wafer W is sucked and held. The plurality of heat transfer gas supply holes 33 are connected to a heat transfer gas supply unit (not shown) via a heat transfer gas supply line 34 disposed inside the mounting table 12. For example, helium (He) gas is supplied to the gap between the adsorption surface and the back surface of the wafer W through the heat transfer gas supply hole 33.

  The mounting table 12 is provided with a plurality of pusher pins 35 as lift pins that can protrude from the upper surface of the mounting table 12. These pusher pins 35 are accommodated in the mounting table 12 when the semiconductor wafer W is sucked and held on the suction surface to perform the etching process. When the semiconductor wafer W is loaded into or unloaded from the mounting table 12, the pusher pin 35 protrudes from the suction surface and supports the semiconductor wafer W on the mounting table 12.

  A shower head 36 having a function as an upper electrode is disposed on the ceiling portion of the processing chamber 11 so as to face the mounting table 12. The shower head 36 and the mounting table 12 function as a pair of electrodes (upper electrode and lower electrode). The shower head 36 includes a disk-shaped cooling plate 38 made of an insulating material, in which a buffer chamber 37 is formed, an upper electrode plate 39 supported by the cooling plate 38, and a lid 40 that covers the cooling plate 38. And.

  The lower surface of the upper electrode plate 39 is exposed in the processing space PS, and is formed in a disk shape made of a conductive material such as silicon. The peripheral edge of the upper electrode plate 39 is covered with an annular shield ring 41 made of an insulating material. That is, the upper electrode plate 39 is electrically insulated by the cooling plate 38 and the shield ring 41 from the wall portion of the processing chamber 11 that is at the ground potential.

  The upper electrode plate 39 is electrically connected to the upper DC power source 42. By applying a negative DC voltage from the upper DC power source 42 to the upper electrode plate 39, a DC voltage is applied to the processing space PS.

  A processing gas introduction pipe 43 is connected to the buffer chamber 37 of the cooling plate 38. The processing gas introduction pipe 43 is connected to a processing gas supply unit (not shown). The shower head 36 is provided with a plurality of through-gas holes 48 that allow the buffer chamber 37 to communicate with the processing space PS. The shower head 36 supplies the processing gas supplied from the processing gas introduction pipe 43 to the buffer chamber 37 to the processing space PS through the through gas hole 48.

  As shown in FIG. 2, a grounding ring 45 (ground electrode) as a DC voltage grounding member having an L-shaped cross section and a ring shape as a whole is disposed in the processing chamber 11. . The ground ring 45 is made of a conductive material, for example, a solid material of silicon or aluminum, and is arranged so that an outer surface thereof is exposed to the processing space PS. The ground ring 45 functions as a ground electrode for a DC voltage applied to the upper electrode plate 39.

  The grounding ring 45 is disposed below the side surface covering member 16 of the mounting table 12 so as to cover the side surface of the mounting table base portion 15a. Therefore, at least the outer portion of the ground ring 45 is exposed to the exhaust flow path 18 portion in the processing space PS. Electrons emitted from the upper electrode plate 39 reach the ground ring 45, and thereby a direct current flows in the processing space PS. The detailed configuration of the ground ring 45 will be described later.

  In the plasma etching apparatus 10 configured as described above, by supplying high-frequency power to the processing space PS, high-density plasma is generated from the processing gas supplied from the shower head 36 in the processing space PS. The generated plasma is kept in a desired state by the direct current, and the wafer W is etched by the plasma.

  As shown in FIG. 3, in this embodiment, the grounding ring 45 is comprised from six circular-arc-shaped members 45a-45f, and is comprised so that the whole may become ring shape. The six arcuate members 45a to 45f have the same size. In other words, one ring-shaped member is divided into six equal parts. In this way, when the grounding ring 45 is constituted by a plurality of arcuate members, it is preferable that at least four or more.

  As shown in FIG. 2, vertical movement mechanisms 50 are disposed on the back surfaces of the arcuate members 45 a to 45 f, respectively. Note that FIG. 2 shows only one of the vertical movement mechanisms 50 provided in total corresponding to the respective arcuate members 45a to 45f.

  The upper end of the drive shaft of the vertical movement mechanism 50 is connected to the back surface of each arcuate member 45a to 45f. The vertical movement mechanism 50 is configured so that each of the arc-shaped members 45a to 45f can be moved up and down independently as indicated by arrows in the drawing. These vertical movement mechanisms 50 have a function of changing the connection state of the arc-shaped members 45a to 45f to the ground potential by moving the arc-shaped members 45a to 45f up and down.

  In the present embodiment, the arcuate members 45a to 45f are in contact with the exhaust plate 19 while being lowered as shown in FIG. 2, and are connected to the ground potential. When the arc-shaped members 45a to 45f are raised by the vertical movement mechanism 50, the connection state to the ground potential is weakened, and the arc-shaped member 45a is raised until it is completely in non-contact with the exhaust plate 19. ˜45f can be set in an electrically floating state.

  Contrary to the above, when the arc-shaped members 45a to 45f are raised, the arc-shaped members 45a to 45f are connected to the ground potential, and when they are lowered, they are electrically floating. You may comprise.

  In addition, as described above, when the grounding ring 45 is composed of a plurality of arcuate members 45a to 45f, the arcuate members 45a to 45f may be electrically connected. Furthermore, as described above, the grounding ring 45 may be formed of a ring-shaped member that is integrally formed, instead of the plurality of arc-shaped members 45a to 45f. Also in this case, a plurality of, for example, at least four vertical movement mechanisms 50 are arranged at regular intervals along the circumferential direction, and the connection state of each part of the ground ring 45 to the ground potential is determined by each vertical movement mechanism 50. Configure to adjust.

In the graphs of FIGS. 4A to 4C, the vertical axis represents the etching rate and the horizontal axis represents the distance from the center of the semiconductor wafer. And the etching rate and uniformity values around (in the radial direction) 3 mm from the edge of the semiconductor wafer W are shown. At this time, the influence which appears in the etching state was investigated by using the ground ring 45 configured integrally and changing the ground state of the ground ring 45. The etching conditions are as follows:
Process gas: CF ₄ / Ar = 50/600 sccm
Pressure: 5.32 Pa (40 mTorr)
High frequency power: 500 / 2000W
DC voltage: 300V
Temperature (mounting table / ceiling and side wall): 20/150 ° C
Helium pressure (center / edge): 1995/5320 Pa (15/40 Torr)
Time: 60 seconds.

  FIG. 4A shows a case in which a spiral electrical connection member for improving the electrical connection state is arranged on the entire back surface side of the ground ring 45. FIG. 4B and FIG. ) Shows a case where an insulating material (made of Kapton) is arranged on the back surface side of the ground ring 45 and the connection state to the ground potential is changed from the case shown in FIG. FIG. 4B shows a case where an insulating material is arranged at a site of 50% on the right side, and FIG. 4C shows a case where an insulating material is arranged on the whole. As shown in FIG. 4B, the in-plane uniformity of the etching rate is changed when the insulating material is arranged at the site of 50% on the right side as compared with the case where the insulating material is not arranged. Further, as shown in FIG. 4C, when the entire ground ring 45 is in a floating state, the in-plane uniformity of the etching rate is remarkably deteriorated, and plasma leaks occur as a phenomenon. Therefore, it is preferable that at least a part of the ground ring 45 is connected to the ground potential.

  The graphs of FIGS. 5A to 5C are based on the results of investigating the effects that appear in the etching state when the tightening torque of the mounting screw at the time of mounting the ground ring 45 is changed, and from the edge of the semiconductor wafer W. It shows the etching rate and uniformity value of the surrounding (diameter direction) contained in 3 mm. FIG. 5A shows a case where the tightening torque is 6 kgf for all the mounting screws, FIG. 5B shows a case where only one mounting screw is used for the tightening torque 6 kgf, and the other is not tightened, and FIG. The case where all the mounting screws were not tightened is shown.

  As shown in the graphs of FIGS. 5 (a) to 5 (c), the in-plane uniformity of etching changes depending on the tightening torque of the mounting screws. The uniformity is clearly worse.

  As described above, it was confirmed that the in-plane uniformity in the circumferential direction of the etching process was changed by partially changing the grounding state of a part of the grounding ring 45. Therefore, in the plasma etching apparatus 10 according to the above embodiment, the grounding state of the arcuate members 45a to 45f constituting the grounding ring 45 is changed by moving the arcuate members 45a to 45f up and down by the vertical movement mechanism 50, The uniformity in the circumferential direction of the etching process can be controlled.

  Next, a procedure for plasma etching the thin film formed on the semiconductor wafer W by the plasma etching apparatus having the above configuration will be described. First, the gate valve 46 is opened, and the semiconductor wafer W is loaded into the processing chamber 11 from the loading / unloading port 44 via a load lock chamber (not shown) by a transfer robot (not shown) and mounted on the mounting table 12. Thereafter, the transfer robot is retracted out of the processing chamber 11 and the gate valve 46 is closed. Then, the inside of the processing chamber 11 is exhausted through the roughing exhaust pipe 20 and the main exhaust pipe 21 by a vacuum pump (not shown).

  After the inside of the processing chamber 11 reaches a predetermined degree of vacuum, a predetermined processing gas (etching gas) is introduced into the processing chamber 11 through the shower head 36, and the processing chamber 11 is maintained at a predetermined pressure. In this state, high-frequency power with a frequency of, for example, 40 MHz is supplied from the first high-frequency power supply 22 to the mounting table 12. Further, from the second high-frequency power source 24, high-frequency power (for bias) having a frequency of, for example, 3.2 MHz is supplied to the mounting table 12 for ion attraction. At this time, a predetermined DC voltage (for example, a DC voltage of plus 2500 V) is applied from the electrostatic chuck DC power supply 28 to the electrode plate 26 of the electrostatic chuck 27, and the semiconductor wafer W is statically applied by Coulomb force or Johnson Rabeck force. Adsorbed to the electric chuck 27.

  As described above, an electric field is formed between the shower head 36 that is the upper electrode and the mounting table 12 that is the lower electrode by applying high-frequency power to the mounting table 12 that is the lower electrode. Due to this electric field, a discharge is generated in the processing space PS in which the semiconductor wafer W exists, and the thin film formed on the semiconductor wafer W is etched by the plasma of the processing gas formed thereby.

  Further, since the DC voltage can be applied from the upper DC power source 42 to the shower head 36 during the plasma processing, the following effects can be obtained. That is, depending on the process, a plasma having a high electron density and low ion energy may be required. If a DC voltage is used in such a case, the ion energy injected into the semiconductor wafer W is suppressed, the plasma electron density is increased, and the etching rate of the film to be etched of the semiconductor wafer W is increased. The sputter rate to the film serving as a mask provided on the upper part of the etching target is lowered, and the selectivity is improved.

  At this time, depending on the attachment state of the ground ring 45 that acts as a ground electrode for the DC voltage applied to the shower head 36, the etching process may be uneven in the circumferential direction. In such a case, conventionally, the processing chamber 11 is opened to the atmosphere, and the mounting state of the grounding ring 45 is adjusted to eliminate processing non-uniformity. On the other hand, in this embodiment, by changing the ground contact state of the arc-shaped members 45a to 45f constituting the ground ring 45 by moving the arc-shaped members 45a to 45f up and down by the vertical movement mechanism 50, Processing non-uniformity can be easily and quickly eliminated without opening the processing chamber 11 to the atmosphere. As a result, a significant improvement in processing efficiency can be realized. Furthermore, the present invention can also be applied to control for reducing the processing bias (machine difference) between the processing chambers 11 and uniformity control at a large diameter (for example, 450 mm).

  When the etching process described above is completed, the supply of high-frequency power, the supply of DC voltage, and the supply of process gas are stopped, and the semiconductor wafer W is unloaded from the process chamber 11 by a procedure reverse to the procedure described above. .

  As described above, according to the present embodiment, the processing bias due to the installation state of the grounding ring 45 as a DC voltage ground member serving as a ground with respect to the DC voltage applied to the shower head 36 as the upper electrode is easily corrected. And uniform processing can be carried out efficiently. Of course, the present invention is not limited to the above-described embodiment, and various modifications are possible.

  W: Semiconductor wafer, 10: Plasma etching apparatus, 11: Processing chamber, 12: Mounting table (lower electrode), 36: Shower head (upper electrode), 42: Upper DC power supply, 45: Grounding Rings, 45a to 45f ... arc-shaped members, 50 ... vertical movement mechanism.

Claims (6)

A processing chamber for forming a processing space therein;
A lower electrode disposed in the processing chamber and also serving as a mounting table on which a substrate to be processed is mounted;
An upper electrode disposed in the processing chamber so as to face the lower electrode;
A high frequency power source for applying high frequency power to the lower electrode;
A DC power supply for applying a DC voltage to the upper electrode;
A processing gas supply mechanism for supplying a processing gas to be converted into plasma into the processing space;
An overall shape is formed in a ring shape from a conductive material, and is disposed in the processing chamber so that at least a part thereof is exposed to the processing space, and forms a ground potential for a DC voltage applied to the upper electrode. A DC voltage ground member;
A plurality of vertical movement mechanisms capable of adjusting the grounding state of the DC voltage ground member by vertically moving the DC voltage ground member ;
A focus ring disposed to surround the substrate to be processed disposed on the lower electrode;
A cover ring disposed so as to surround the outer periphery of the focus ring;
Comprising
The DC voltage ground member is disposed on a side surface of the lower electrode so as to surround the lower electrode at a position lower than the cover ring, and is electrically floating or grounded when raised. Plasma processing equipment. The plasma processing apparatus according to claim 1,
The plasma processing apparatus, wherein the DC voltage ground member is made of silicon. The plasma processing apparatus according to claim 1,
The plasma processing apparatus, wherein the DC voltage ground member is formed of a solid aluminum material. The plasma processing apparatus according to any one of claims 1 to 3,
The plasma processing apparatus, wherein the plurality of vertical movement mechanisms are independently movable up and down . A plasma processing apparatus according to any one of claims 1 to 4,
The plasma processing apparatus, wherein the DC voltage ground member is formed from a plurality of arc-shaped members so as to form a ring shape as a whole, and the vertical movement mechanism is provided for each arc-shaped member. . The plasma processing apparatus according to claim 5, wherein
The plasma processing apparatus, wherein the DC voltage ground member comprises at least four arc-shaped members.

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